The present invention relates to a multi-mode exercising apparatus for providing exercise in isometric, isotonic, isokinetic and constant power modes.
In isometric exercises the rate of angular change or velocity of the limb is zero, while the force can be in either of two directions. In an isotonic mode the load or resistive force has a constant value while the velocity varies. In an isokinetic mode the force is allowed to vary to match the user's force in such a way that the velocity is kept constant. Finally, in a constant power mode both velocity and force are allowed to vary such that their product is kept constant. In any of the latter three modes a muscle may undergo either a concentric contraction in which the muscle is developing force while it is shortening in length, or an eccentric contraction in which the muscle is developing force while it is increasing in length. By way of example, in a concentric stroke the user moves the arm or limb of the exercising machine while in an eccentric stroke the arm attempts to move the limb of the user.
Exercise apparatus exists which provide a constant force load by means of weighted plates or springs over the whole range of movement of the limb. Since the muscle is generally strongest over a relatively narrow range of such movement, fixed load or constant force devices do not optimally load a muscle through its entire range of movement. A device which does load a muscle on an approximate constant velocity basis is disclosed in U.S. Pat. No. 3,465,592, issued to Perrine on Sept. 9, 1969. The Perrine device employs a hydraulic piston-cylinder in combination with a constant flow valve and an associated valving system to provide a constant flow through one side or the other of the hydraulic piston-cylinder. A pressure valve measuring fluid pressure is used to measure user applied force. Perrine also discloses an alternative embodiment employing an electric motor and a gearing system and clutches to couple user torque to a worm gear being rotated by a motor at a constant velocity. The latter device is restricted to either an isometric or an approximate constant velocity mode and to concentric exercises rather than both concentric and eccentric exercises. Moreover, the Perrine device includes in its measurement of the force the weight of the handle and arm linkage and resistance caused by friction.
U.S. Pat. No. 3,784,194 issued Jan. 8, 1974 to Perrine discloses the use of a fluid operated actuator in combination with a system of overlapping valve holes for setting the rate of fluid flow and consequent velocity. The latter device again is restricted to an approximate constant velocity mode and is subject to the other limitations expressed in connection with the above-mentioned earlier Perrine patent.